Asked by an activist yesterday about why he failed to mention tuition fees during a speech in Swindon, Mr Corbyn replied: "It's coming in, yeah, we've just got to figure out the wording of it."

He also brushed off speculation about his future as Labour leader as "absurd".

It came as Theresa May, the Prime Minister, yesterday signalled her support for tuition fees which currently stand at £9,000.

Asked about rising tuition fees and how she could ensure that "university is affordable for all", Mrs May replied: “When the tuition fees came in, a lot of people said that what they thought might happen was actually young people from less advantaged families might be less likely to go to university.

“In fact, that’s not the case – the reverse has happened. So I think we have seen [people] crucially still being able to take those university opportunities.”

But she added that university is not the "right route for everyone" and spoke of the need to offer more apprenticeships around the UK.

Ed Miliband, the previous Labour leader, stood on a pledge to cut tuition fees from £9,000 to £6,000 but concerns were raised about how the party would fund such an expensive commitment.

View photos

Theresa MayCredit: Getty

Mr Corbyn also pledged to increase the minimum wage to £10 yesterday.

It came as details emerged of a discussion about campaign slogans and rebuttals which saw the phrase "The Tories are the real extremists" ruled out by senior party officials.

It was part of a presentation by Steve Howell and Seumas Milne, Mr Corbyn's most senior advisors, which also included lines of defence against Tory attacks and key discussion topics ahead of the vote.

Mr Howell talked party figures through a number of different campaign straplines which could be used during the General Election including another about how the Conservatives are working for millionaires but Labour wants to make the country richer, sources at the meeting said.

View photos

The Labour leaderCredit: PA

However some members of the ruling committee raised concerns about linking Theresa May to extremism because of the questions it might raise about Mr Corbyn's own record.

The phrase was suggested as a way to counter Tory attacks but it was later ruled out by Mr Corbyn's director of communications Seumas Milne, it is understood.

It follows a document published by the party earlier this week which sought to reassure voters that Mr Corbyn is not a "terrorist sympathiser".

It stated: "Jeremy has always believed that war needs to be last course of action and peace is always preferable.

"Like many politicians during the troubles with the IRA, Jeremy was attempting to bring together both sides to broker peace and his belief in transparency meant that unlike other politicians he did not keep this secret.

"Despite the hysteria around Jeremy’s interest in diplomacy these ideas are not new – indeed in 2009, David Miliband spoke of drawing from our experiences with the IRA to engage in talks with ‘moderate elements’ of the Taliban."

Earlier in the day Labour put out a tweet calling for potential candidates to come forward and fill seats where MPs are standing down.

The UK Labour official account wrote: "Could you be a brilliant local MP? We’re looking for parliamentary candidates for the #GeneralElection. Apply now."